1. Field of the Invention
The present invention relates generally to a fixation instrument for repairing bone fractures. More specifically, to a bone nail having a self entry feature.
2. Description of Related Art
Orthopedic fixation systems used for stabilizing a fracture often include an internal fixation device, typically an elongated implant such as a nail, screw or pin, inserted into the intramedullary canal of the bone to stabilize the fracture and promote healing. Humeral shaft fractures, like many bone fractures can be treated with a nail.
Typically a humeral nail is inserted into the humerus by first making an entry hole in the end thereof. The entry hole is made using either a drill or an awl to cut a hole, typically about 2 mm in diameter, in the cortical bone. Once an entry hole is made, a guide wire is inserted into the bone and extends through the entry hole into the bone past the fracture site. The guide wire helps to align the fracture.
A reamer is used to open the entry hole, along with the interior or intramedullary canal of the humerus, to form a passageway for the humeral nail. Typically the reamer opens a passageway in the cortical bone and the marrow space or intramedullary canal, approximately 1 to 1.5 millimeters larger than the overall diameter of the nail to be used. Once the reaming procedure is complete, the nail is attached to an insertion tool and is threaded over the guide wire. The nail is inserted into the bone, along the guide wire until it extends past and spans both sides of the fracture. Once the nail is properly aligned within the humerus, bone screws are inserted transversely through the bone and are received in openings or passageways located at or near the proximal and distal ends of the nail.
While reaming helps to open the bone and allow easier insertion of the humeral nail, it also requires an extra step. Further, in many cases if too much of the soft, spongy bone is removed, it may disrupt the blood supply within the humerus. Finally, if the entry hole and passageway has too great a diameter, the nail may move about within the interior of the bone.